1. Field of the Invention
The invention relates generally to visual positioning systems and, more particularly, to visual positioning systems that utilize images of a working environment to determine position.
2. Background Information
Machine control systems may utilize global navigation satellite system (GNSS) receivers to determine the global position of machinery, and inertial and other sensors may be added to provide information relating to the orientation and movement of the machinery. The GNSS receivers and inertial and other sensors update the position and orientation information to aid a driver or a robotic control in navigating the machine to a desired location or along a desired route, and so forth. These systems work well in many, but not all, environments. For example, the GNSS receivers may not work well in environments that include multiple nearby sources of multipath signals and/or in environments without sufficiently clear views of the sky, such as indoors.
Other systems, such as cellular telephone systems, may determine positions utilizing triangulation with cellular towers based on signal strength and so forth. The cellular systems, however, require infrastructure that may not be available or may not operate well in the working environments of interest.
In certain working environments, such as warehouses, farm fields and so forth, accurate relative positions as opposed to global positions are sufficient to control the operation of machinery moving within the environment. Accordingly, in certain of the working environments, accurate positioning systems with little or no infrastructure may be particularly useful alone or in conjunction with global positioning systems.